We have measured axonal transport of dopamine-beta-hydroxylase (DBH) in human sural nerve biopsies incubated in vitro. Transport proceeds linearily for several hours under these conditions. We have noticed a marked deficity in transport in nerves from patients with various peripheral neuropathies. A careful examination of the temporal relations between loss of transport, loss of enzyme levels, and loss of function is contemplated in human nerve diseases and animal models for these diseases. Investigations on the subcellular distribution of DBH in rat sciatic nerves have indicated that there may be different types of particles containing DBH in these axons and that these particles may have different origins and fates. We are currently analyzing axonal transport of different subcellular forms of DBH in order to shed more light on this possibility.